ref: 0dd7d2c206eecd6f423d557a16af3e5d07a7b1d3
parent: 2fde5c7c3678b14200e91b7ea1fd04b6a75a08f7
author: robs <robs>
date: Tue Jan 16 17:22:39 EST 2007
Variable Q for low/high pass filters; made common 1,2 pole interface.
--- a/ChangeLog
+++ b/ChangeLog
@@ -20,14 +20,14 @@
o Add FLAC support (robs@users.sf.net)
o Allow encoding quality to be specified (works for Ogg too, but not
MP3).
- o bass and treble altering effects. (robs@users.sf.net)
- o Visualisation of various filters' frequency response via Octave.
- (robs@users.sf.net)
o Allow the rate and number of channels of .au files to be overridden
by command-line arguments. (robs@users.sf.net)
o More and better self-tests. (robs@users.sf.net)
o Support Maxis's XA format. (Dwayne C. Litzenberger)
o Add equalizer effect (Pascal Giard)
+ o bass and treble altering effects. (robs)
+ o Documented the butterworth filter effects; added variable Q. (robs)
+ o Visualisation of various filters' frequency response via Octave. (robs)
o Fix rounding error when reading command-line time
parameters. (robs)
o Allow command-line time parameters of < 1 sec to omit the
@@ -62,7 +62,6 @@
resample, and rate has been removed.
o Improved synth usage (by introducing --) and improved the synth
entry in the man-page. (robs)
- o Documented the butterworth filter effects. (robs)
o Added command line options for specifying the output file
comment. (robs)
o Improved the accuracy of integer and floating point PCM
--- a/sox.1
+++ b/sox.1
@@ -1344,25 +1344,39 @@
.TE
.SP
.TP
-\fBhighp\fR\^|\^\fBlowp \fIfrequency\fR
-Apply a single-pole recursive high-pass or low-pass filter with
-3dB point \fIfrequency\fR.
-The filters roll off at 6dB per octave (20dB per decade).
+\fBhighp\fR \fIfrequency\fR
+Apply a high-pass filter.
+This effect is just an alias for the
+.B highpass
+effect used with its
+.B -1
+option; it is retained for backwards compatibilty only.
+.TP
+\fBhighpass\fR\^|\^\fBlowpass\fR [\fB-1\fR|\fB-2\fR] \fIfrequency\fR [\fIQ\fR]
+Apply a high-pass or low-pass filter with 3dB point \fIfrequency\fR.
+The filter can be either single-pole (with
+.BR -1 ),
+or double-pole (with
+.B -2
+or if unspecified).
+.I Q
+applies only to double-pole filters; its default value is 0\*d707 and gives
+a Butterworth response. The single-pole and double-pole filters roll off at
+6 and 12 dB per octave (20 and 40 dB per decade) respectively. See
+http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt for a detailed
+discussion of the double-pole filters.
.SP
These effects support the \fB\-\-octave\fR global option (see above).
.SP
See also \fBfilter\fR for filters with a sharper cutoff.
.TP
-\fBhighpass\fR\^|\^\fBlowpass \fIfrequency\fR
-Apply a two-pole Butterworth high-pass or low-pass filter with
-3dB point \fIfrequency\fR.
-The filters roll off at 12dB per octave (40dB per decade).
-.SP
-These effects support the \fB\-\-octave\fR global option (see above).
-.TP
\fBlowp \fIfrequency\fR
Apply a low-pass filter.
-See the description of the \fBhighp\fR effect for details.
+This effect is just an alias for the
+.B lowpass
+effect used with its
+.B -1
+option; it is retained for backwards compatibilty only.
.TP
\fBlowpass \fIfrequency\fR
Apply a low-pass filter.
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -20,14 +20,14 @@
raw.c sf.c sfircam.h skelform.c smp.c sndrtool.c sphere.c tx16w.c voc.c \
vorbis.c vox.c wav.c wav.h wve.c xa.c
-effects = avg.c band.c bandpass.c biquad.c biquad.h breject.c btrworth.c \
- btrworth.h chorus.c compand.c dcshift.c deemphas.c earwax.c \
- echo.c echos.c equalizer.c fade.c FFT.c FFT.h filter.c flanger.c \
- highp.c highpass.c lowp.c lowpass.c luaeff.c luaform.c \
- lintlib.c mask.c mcompand.c noiseprof.c noisered.c noisered.h \
- pad.c pan.c phaser.c pitch.c polyphas.c rabbit.c rate.c repeat.c \
- resample.c reverb.c reverse.c silence.c skeleff.c speed.c stat.c \
- stretch.c swap.c synth.c tone.c trim.c vibro.c vol.c
+effects = avg.c band.c bandpass.c biquad.c biquad.h biquadlh.c breject.c \
+ btrworth.c btrworth.h chorus.c compand.c dcshift.c deemphas.c \
+ earwax.c echo.c echos.c equalizer.c fade.c FFT.c FFT.h filter.c \
+ flanger.c luaeff.c luaform.c lintlib.c mask.c mcompand.c \
+ noiseprof.c noisered.c noisered.h pad.c pan.c phaser.c pitch.c \
+ polyphas.c rabbit.c rate.c repeat.c resample.c reverb.c reverse.c \
+ silence.c skeleff.c speed.c stat.c stretch.c swap.c synth.c tone.c \
+ trim.c vibro.c vol.c
libst_la_SOURCES = $(formats) $(effects) alsa.c oss.c sunaudio.c handlers.c misc.c \
st_i.h stio.c stlua.c util.c xmalloc.c xmalloc.h getopt.c getopt1.c getopt.h
--- /dev/null
+++ b/src/biquadlh.c
@@ -1,0 +1,180 @@
+/*
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library. If not, write to the Free Software Foundation,
+ * Fifth Floor, 51 Franklin Street, Boston, MA 02111-1301, USA.
+ */
+
+/* Sound Tools Effects: 2-pole variable Q & 1-pole low/high-pass filters.
+ *
+ * This implementation (c) 2007 robs@users.sourceforge.net
+ *
+ * 2-pole with default Q gives a Butterworth response.
+ *
+ * 2-pole filter design by Robert Bristow-Johnson <rbj@audioimagination.com>
+ * see http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt
+ *
+ * 1-pole low-pass based on lowp.c:
+ * (c) 2000 Chris Bagwell <cbagwell@sprynet.com>
+ *
+ * Algorithm: Recursive single pole lowpass filter
+ *
+ * Reference: The Scientist and Engineer's Guide to Digital Signal Processing
+ *
+ * output[N] = input[N] * A + output[N-1] * B
+ *
+ * X = exp(-2.0 * pi * Fc)
+ * A = 1 - X
+ * B = X
+ * Fc = cutoff freq / sample rate
+ *
+ * Mimics an RC low-pass filter:
+ *
+ * ---/\/\/\/\----------->
+ * |
+ * --- C
+ * ---
+ * |
+ * |
+ * V
+ *
+ * 1-pole high-pass based on highp.c:
+ * (c) 2000 Chris Bagwell <cbagwell@sprynet.com>
+ *
+ * Algorithm: Recursive single pole high-pass filter
+ *
+ * Reference: The Scientist and Engineer's Guide to Digital Processing
+ *
+ * output[N] = A0 * input[N] + A1 * input[N-1] + B1 * output[N-1]
+ *
+ * X = exp(-2.0 * pi * Fc)
+ * A0 = (1 + X) / 2
+ * A1 = -(1 + X) / 2
+ * B1 = X
+ * Fc = cutoff freq / sample rate
+ *
+ * Mimics an RC high-pass filter:
+ *
+ * || C
+ * ----||--------->
+ * || |
+ * <
+ * > R
+ * <
+ * |
+ * V
+ */
+
+#include "biquad.h"
+#include <string.h>
+#undef st_fail
+#define st_fail st_message_filename=effp->name,st_fail
+
+static int getopts(eff_t effp, int n, char **argv)
+{+ biquad_t p = (biquad_t) effp->priv;
+ char dummy;
+ char order;
+
+ if (n != 0 && sscanf(argv[0], "-%1[12] %c", &order, &dummy) == 1)
+ ++argv, --n;
+ else order = strlen(effp->name) <= 5 /* lowp|highp */ ? '1' : '2';
+ order -= '0';
+
+ p->width.q = order == 2? sqrt(0.5) : 0;
+ if (n < 1 || n > order || sscanf(argv[0], "%lf %c", &p->fc, &dummy) != 1 ||
+ p->fc <= 0 || (n == 2 && (sscanf(argv[1], "%lf %c", &p->width.q, &dummy)
+ != 1 || p->width.q <= 0))) {+ st_fail(effp->h->usage);
+ return ST_EOF;
+ }
+ return ST_SUCCESS;
+}
+
+static int start(eff_t effp)
+{+ biquad_t p = (biquad_t) effp->priv;
+ double w0 = 2 * M_PI * p->fc / effp->ininfo.rate;
+
+ if (w0 > M_PI) {+ st_fail("cut-off frequency must be less than half the sample-rate (Nyquist rate)");+ return ST_EOF;
+ }
+ if (p->width.q) { /* 2-pole */+ double alpha = sin(w0)/(2*p->width.q);
+
+ if (*effp->name == 'l') { /* lowpass */+ p->b0 = (1 - cos(w0))/2;
+ p->b1 = 1 - cos(w0);
+ p->b2 = (1 - cos(w0))/2;
+ } else {+ p->b0 = (1 + cos(w0))/2;
+ p->b1 = -(1 + cos(w0));
+ p->b2 = (1 + cos(w0))/2;
+ }
+ p->a0 = 1 + alpha;
+ p->a1 = -2*cos(w0);
+ p->a2 = 1 - alpha;
+ } else { /* 1-pole */+ p->a0 = 1;
+ p->a1 = -exp(-w0);
+ if (*effp->name == 'l') { /* lowpass */+ p->b0 = 1 + p->a1;
+ p->b1 = 0;
+ } else {+ p->b0 = (1 - p->a1)/2;
+ p->b1 = -p->b0;
+ }
+ p->a2 = p->b2 = 0;
+ }
+ return st_biquad_start(effp, "Q");
+}
+
+st_effect_t const * st_lowp_effect_fn(void)
+{+ static st_effect_t driver = {+ "lowp", "Usage: lowp cutoff", 0,
+ getopts, start, st_biquad_flow,
+ st_effect_nothing_drain, st_effect_nothing, st_effect_nothing
+ };
+ return &driver;
+}
+
+st_effect_t const * st_highp_effect_fn(void)
+{+ static st_effect_t driver = {+ "highp", "Usage: highp cutoff", 0,
+ getopts, start, st_biquad_flow,
+ st_effect_nothing_drain, st_effect_nothing, st_effect_nothing
+ };
+ return &driver;
+}
+
+st_effect_t const * st_lowpass_effect_fn(void)
+{+ static st_effect_t driver = {+ "lowpass", "Usage: lowpass [-1|-2] frequency [Q]", 0,
+ getopts, start, st_biquad_flow,
+ st_effect_nothing_drain, st_effect_nothing, st_effect_nothing
+ };
+ return &driver;
+}
+
+st_effect_t const * st_highpass_effect_fn(void)
+{+ static st_effect_t driver = {+ "highpass", "Usage: highpass [-1|-2] frequency [Q]", 0,
+ getopts, start, st_biquad_flow,
+ st_effect_nothing_drain, st_effect_nothing, st_effect_nothing
+ };
+ return &driver;
+}
--- a/src/flanger.c
+++ b/src/flanger.c
@@ -1,9 +1,20 @@
-/* Sound Tools Effect: Stereo Flanger
+/*
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
*
- * (c) 2006 robs@users.sourceforge.net
+ * This library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
+ * General Public License for more details.
*
- * See LICENSE file for further copyright information.
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library. If not, write to the Free Software Foundation,
+ * Fifth Floor, 51 Franklin Street, Boston, MA 02111-1301, USA.
*/
+
+/* Effect: Stereo Flanger (c) 2006 robs@users.sourceforge.net */
#define st_flanger_usage \
"Usage: flanger [delay depth regen width speed shape phase interp]\n"
--- a/src/highp.c
+++ /dev/null
@@ -1,143 +1,0 @@
-/*
- * Sound Tools High-Pass effect file.
- *
- * (C) 2000 Chris Bagwell <cbagwell@sprynet.com>
- * See License file for further copyright information.
- *
- * Algorithm: Recursive single pole high-pass filter
- *
- * Reference: The Scientist and Engineer's Guide to Digital Processing
- *
- * output[N] = A0 * input[N] + A1 * input[N-1] + B1 * output[N-1]
- *
- * X = exp(-2.0 * pi * Fc)
- * A0 = (1 + X) / 2
- * A1 = -(1 + X) / 2
- * B1 = X
- * Fc = cutoff freq / sample rate
- *
- * Mimics an RC high-pass filter:
- *
- * || C
- * ----||--------->
- * || |
- * <
- * > R
- * <
- * |
- * V
- *
- */
-
-#include <math.h>
-#include "st_i.h"
-
-static st_effect_t st_highp_effect;
-
-/* Private data for Highpass effect */
-typedef struct highpstuff {- float cutoff;
- double A0, A1, B1;
- double inm1, outm1;
-} *highp_t;
-
-/*
- * Process options
- */
-static int st_highp_getopts(eff_t effp, int n, char **argv)
-{- highp_t highp = (highp_t) effp->priv;
-
- if ((n < 1) || !sscanf(argv[0], "%f", &highp->cutoff))
- {- st_fail(st_highp_effect.usage);
- return (ST_EOF);
- }
- return (ST_SUCCESS);
-}
-
-/*
- * Prepare processing.
- */
-static int st_highp_start(eff_t effp)
-{- highp_t highp = (highp_t) effp->priv;
- if (highp->cutoff > effp->ininfo.rate/2)
- {- st_fail("Highpass: cutoff must be < sample rate / 2 (Nyquest rate)");- return (ST_EOF);
- }
-
- highp->B1 = exp((-2.0 * M_PI * (highp->cutoff / effp->ininfo.rate)));
- highp->A0 = (1 + highp->B1) / 2;
- highp->A1 = (-1 * (1 + highp->B1)) / 2;
- highp->inm1 = 0.0;
- highp->outm1 = 0.0;
-
- if (effp->globalinfo->octave_plot_effect)
- {- printf(
- "title('SoX effect: %s cutoff=%g (rate=%u)')\n"- "xlabel('Frequency (Hz)')\n"- "ylabel('Amplitude Response (dB)')\n"- "Fs=%u;minF=10;maxF=Fs/2;\n"
- "axis([minF maxF -95 5])\n"
- "sweepF=logspace(log10(minF),log10(maxF),200);\n"
- "grid on\n"
- "[h,w]=freqz([%f %f],[1 %f],sweepF,Fs);\n"
- "semilogx(w,20*log10(h),'b')\n"
- "pause\n"
- , effp->name, highp->cutoff
- , effp->ininfo.rate, effp->ininfo.rate
- , highp->A0, highp->A1, -highp->B1
- );
- return ST_EOF;
- }
- return (ST_SUCCESS);
-}
-
-/*
- * Processed signed long samples from ibuf to obuf.
- * Return number of samples processed.
- */
-static int st_highp_flow(eff_t effp, const st_sample_t *ibuf, st_sample_t *obuf,
- st_size_t *isamp, st_size_t *osamp)
-{- highp_t highp = (highp_t) effp->priv;
- int len, done;
- double d;
- st_sample_t l;
-
- len = ((*isamp > *osamp) ? *osamp : *isamp);
-
- for(done = 0; done < len; done++) {- l = *ibuf++;
- d = highp->A0 * l +
- highp->A1 * highp->inm1 +
- highp->B1 * highp->outm1;
- ST_SAMPLE_CLIP_COUNT(d, effp->clips);
- highp->inm1 = l;
- highp->outm1 = d;
- *obuf++ = d;
- }
- *isamp = len;
- *osamp = len;
- return (ST_SUCCESS);
-}
-
-static st_effect_t st_highp_effect = {- "highp",
- "Usage: highp cutoff",
- 0,
- st_highp_getopts,
- st_highp_start,
- st_highp_flow,
- st_effect_nothing_drain,
- st_effect_nothing,
- st_effect_nothing
-};
-
-const st_effect_t *st_highp_effect_fn(void)
-{- return &st_highp_effect;
-}
--- a/src/highpass.c
+++ /dev/null
@@ -1,90 +1,0 @@
-/*
- High-pass effect file for SoX
- Copyright (C) 1999 Jan Paul Schmidt <jps@fundament.org>
-
- This library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation; either
- version 2 of the License, or (at your option) any later version.
-
- This library is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public
- License along with this library; if not, write to the Free Software
- Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-
- Code based on the high-pass implementation in
-
- Sound Processing Kit - A C++ Class Library for Audio Signal Processing
- Copyright (C) 1995-1998 Kai Lassfolk
-
- as described in
-
- Computer music: synthesis, composition, and performance
- Charles Dodge, Thomas A. Jerse
- [2nd ed.]
- Page 215
-
- */
-
-#include <math.h>
-
-#include "st_i.h"
-#include "btrworth.h"
-
-static st_effect_t st_highpass_effect;
-
-static int st_highpass_getopts(eff_t effp, int n, char **argv)
-{- butterworth_t butterworth = (butterworth_t)effp->priv;
-
- if (n != 1) {- st_fail(st_highpass_effect.usage);
- return (ST_EOF);
- }
-
- st_butterworth_start (effp);
-
- if (!(sscanf (argv [0], "%lf", &butterworth->frequency))) {- st_fail("highpass: illegal frequency");- return (ST_EOF);
- }
- return (ST_SUCCESS);
-}
-
-static int st_highpass_start(eff_t effp)
-{- butterworth_t butterworth = (butterworth_t) effp->priv;
- double c;
-
- c = tan (M_PI * butterworth->frequency / effp->ininfo.rate);
-
- butterworth->a [0] = 1.0 / (1.0 + sqrt (2.0) * c + c * c);
- butterworth->a [1] = -2.0 * butterworth->a [0];
- butterworth->a [2] = butterworth->a [0];
-
- butterworth->b [0] = 2 * (c * c - 1.0) * butterworth->a[0];
- butterworth->b [1] = (1.0 - sqrt(2.0) * c + c * c) * butterworth->a [0];
- st_butterworth_plot(effp);
- return (ST_SUCCESS);
-}
-
-static st_effect_t st_highpass_effect = {- "highpass",
- "Usage: highpass FREQUENCY",
- 0,
- st_highpass_getopts,
- st_highpass_start,
- st_butterworth_flow,
- st_effect_nothing_drain,
- st_effect_nothing,
- st_effect_nothing
-};
-
-const st_effect_t *st_highpass_effect_fn(void)
-{- return &st_highpass_effect;
-}
--- a/src/lowp.c
+++ /dev/null
@@ -1,136 +1,0 @@
-/*
- * Sound Tools Low-Pass effect file.
- *
- * (C) 2000 Chris Bagwell <cbagwell@sprynet.com>
- * See License file for further copyright information.
- *
- * Algorithm: Recursive single pole lowpass filter
- *
- * Reference: The Scientist and Engineer's Guide to Digital Signal Processing
- *
- * output[N] = input[N] * A + output[N-1] * B
- *
- * X = exp(-2.0 * pi * Fc)
- * A = 1 - X
- * B = X
- * Fc = cutoff freq / sample rate
- *
- * Mimics an RC low-pass filter:
- *
- * ---/\/\/\/\----------->
- * |
- * --- C
- * ---
- * |
- * |
- * V
- *
- */
-
-#include <math.h>
-#include "st_i.h"
-
-static st_effect_t st_lowp_effect;
-
-/* Private data for Lowpass effect */
-typedef struct lowpstuff {- float cutoff;
- double A, B;
- double outm1;
-} *lowp_t;
-
-/*
- * Process options
- */
-static int st_lowp_getopts(eff_t effp, int n, char **argv)
-{- lowp_t lowp = (lowp_t) effp->priv;
-
- if ((n < 1) || !sscanf(argv[0], "%f", &lowp->cutoff))
- {- st_fail(st_lowp_effect.usage);
- return (ST_EOF);
- }
- return (ST_SUCCESS);
-}
-
-/*
- * Prepare processing.
- */
-static int st_lowp_start(eff_t effp)
-{- lowp_t lowp = (lowp_t) effp->priv;
- if (lowp->cutoff > effp->ininfo.rate / 2)
- {- st_fail("Lowpass: cutoff must be < sample rate / 2 (Nyquest rate)");- return (ST_EOF);
- }
-
- lowp->B = exp((-2.0 * M_PI * (lowp->cutoff / effp->ininfo.rate)));
- lowp->A = 1 - lowp->B;
- lowp->outm1 = 0.0;
-
- if (effp->globalinfo->octave_plot_effect)
- {- printf(
- "title('SoX effect: %s cutoff=%g (rate=%u)')\n"- "xlabel('Frequency (Hz)')\n"- "ylabel('Amplitude Response (dB)')\n"- "Fs=%u;minF=10;maxF=Fs/2;\n"
- "axis([minF maxF -95 5])\n"
- "sweepF=logspace(log10(minF),log10(maxF),200);\n"
- "grid on\n"
- "[h,w]=freqz([%f 0],[1 %f],sweepF,Fs);\n"
- "semilogx(w,20*log10(h),'b')\n"
- "pause\n"
- , effp->name, lowp->cutoff
- , effp->ininfo.rate, effp->ininfo.rate
- , lowp->A, -lowp->B
- );
- return ST_EOF;
- }
- return (ST_SUCCESS);
-}
-
-/*
- * Processed signed long samples from ibuf to obuf.
- * Return number of samples processed.
- */
-static int st_lowp_flow(eff_t effp, const st_sample_t *ibuf, st_sample_t *obuf,
- st_size_t *isamp, st_size_t *osamp)
-{- lowp_t lowp = (lowp_t) effp->priv;
- int len, done;
- double d;
- st_sample_t l;
-
- len = ((*isamp > *osamp) ? *osamp : *isamp);
-
- for(done = 0; done < len; done++) {- l = *ibuf++;
- d = lowp->A * l + lowp->B * lowp->outm1;
- ST_SAMPLE_CLIP_COUNT(d, effp->clips);
- lowp->outm1 = d;
- *obuf++ = d;
- }
- *isamp = len;
- *osamp = len;
- return (ST_SUCCESS);
-}
-
-static st_effect_t st_lowp_effect = {- "lowp",
- "Usage: lowp cutoff",
- 0,
- st_lowp_getopts,
- st_lowp_start,
- st_lowp_flow,
- st_effect_nothing_drain,
- st_effect_nothing,
- st_effect_nothing
-};
-
-const st_effect_t *st_lowp_effect_fn(void)
-{- return &st_lowp_effect;
-}
--- a/src/lowpass.c
+++ /dev/null
@@ -1,79 +1,0 @@
-/*
-
- Low-pass effect file for SoX
- Copyright (C) 1999 Jan Paul Schmidt <jps@fundament.org>
-
- This library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation; either
- version 2 of the License, or (at your option) any later version.
-
- This library is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public
- License along with this library; if not, write to the Free Software
- Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-
- */
-
-#include <math.h>
-
-#include "st_i.h"
-#include "btrworth.h"
-
-static st_effect_t st_lowpass_effect;
-
-static int st_lowpass_getopts(eff_t effp, int n, char **argv)
-{- butterworth_t butterworth = (butterworth_t)effp->priv;
-
- if (n != 1) {- st_fail(st_lowpass_effect.usage);
- return (ST_EOF);
- }
-
- st_butterworth_start (effp);
-
- if (!(sscanf (argv [0], "%lf", &butterworth->frequency))) {- st_fail("lowpass: illegal frequency");- return (ST_EOF);
- }
- return (ST_SUCCESS);
-}
-
-static int st_lowpass_start(eff_t effp)
-{- butterworth_t butterworth = (butterworth_t) effp->priv;
- double c;
-
- c = 1.0 / tan (M_PI * butterworth->frequency / effp->ininfo.rate);
-
- butterworth->a [0] = 1.0 / (1.0 + sqrt(2.0) * c + c * c);
- butterworth->a [1] = 2.0 * butterworth->a [0];
- butterworth->a [2] = butterworth->a [0];
-
- butterworth->b [0] = 2 * (1.0 - c * c) * butterworth->a[0];
- butterworth->b [1] = (1.0 - sqrt(2.0) * c + c * c) * butterworth->a [0];
- st_butterworth_plot(effp);
- return (ST_SUCCESS);
-}
-
-static st_effect_t st_lowpass_effect = {- "lowpass",
- "Usage: lowpass FREQUENCY",
- 0,
- st_lowpass_getopts,
- st_lowpass_start,
- st_butterworth_flow,
- st_effect_nothing_drain,
- st_effect_nothing,
- st_effect_nothing
-};
-
-const st_effect_t *st_lowpass_effect_fn(void)
-{- return &st_lowpass_effect;
-}
--- a/src/pad.c
+++ b/src/pad.c
@@ -1,18 +1,17 @@
/*
- * This library is free software; you can redistribute it and/or modify
- * it under the terms of the GNU Lesser General Public License as
- * published by the Free Software Foundation; either version 2 of the
- * License, or (at your option) any later version.
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
+ * General Public License for more details.
*
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library. If not, write to the Free Software
- * Foundation, Fifth Floor, 51 Franklin Street, Boston, MA 02111-1301,
- * USA.
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library. If not, write to the Free Software Foundation,
+ * Fifth Floor, 51 Franklin Street, Boston, MA 02111-1301, USA.
*/
/* Effect: Pad With Silence (c) 2006 robs@users.sourceforge.net */